Transseptal needle

ABSTRACT

Embodiments of medical devices and methods are disclosed. The medical devices typically comprises a needle with a rigid proximal shaft, a flexible distal shaft and a distal tip. The distal tip includes an electrode for delivering energy to puncture a tissue. In some embodiments, the distal shaft comprises a superelastic material. In other embodiments, the distal shaft is comprised of both a superelastic material and a non-superelastic material.

TECHNICAL FIELD

The disclosure generally relates to the field of medical devices and methods for accessing interior anatomy. More specifically, the disclosure relates to surgical needles.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be readily understood, embodiments of the invention are illustrated by way of examples in the accompanying drawings:

FIG. 1 is a top view of a needle assembly in accordance with an embodiment of the present invention;

FIG. 2 is a cross-sectional side view of the distal portion of a needle having an overlapping tube configuration in accordance with an embodiment of the present invention;

FIG. 3 is a cross-sectional side view of a tapered distal portion of a needle having an end-to-end tube configuration in accordance with an embodiment of the present invention;

FIG. 4 is a cross-sectional side view of a non-tapered distal portion of a needle having an end-to-end tube configuration in accordance with an embodiment of the present invention;

FIG. 5 is a cross-sectional side view of the distal portion of a needle having an interlocking joint in accordance with an embodiment of the present invention;

FIG. 6 is a cross-sectional side view of the distal portion of a needle having an overlapping hinge;

FIG. 7 is a cross-sectional side view of the distal portion of a needle having an end-to-end hinge;

FIG. 8 is a cross-sectional side view of the distal portion of a needle having a combined overlapping and end-to-end hinge;

FIG. 9 is a cross-sectional side view of the distal portion of a needle having a hybrid distal shaft;

FIG. 10, in perspective view, shows an electrode configuration with an open end usable in the various embodiments of the needle;

FIG. 11, in perspective view, shows an electrode configuration with an external component end usable in the various embodiments of the needle; and

FIG. 12, in a partially cut-away view, illustrates an embodiment of the needle having an internal support wire.

DETAILED DESCRIPTION

Some transseptal needles are comprised of separate proximal and distal shaft sections comprised of steel and joined at a shaft junction. This junction or joint where the proximal and distal shaft sections meet can bend or even break when mechanically loaded during use. For example, a distal shaft section can break when a physician loads the needle into a dilator, or when a physician bends a distal portion of the needle (manually or by using mechanical pliers) to create a distal curve. If the tip (or distal shaft) of a Brockenbrough/transseptal needle separates from the main/proximal shaft during a procedure, it may become lost inside of a patient.

It is desirable that a transseptal needle be resistant to unintentional permanent bending and fatigue failure at the junction of the proximal and distal shafts without compromising overall device performance.

The present inventors have conceived and reduced to practice embodiments of a surgical puncturing device, or needle assembly, wherein at least a part/portion of a distal shaft is superelastic. Such a distal shaft is more tolerant to stress than a similar sized distal shaft comprised of only non-superelastic material (e.g. steel). In most cases, when subjected to a mechanical load, the superelastic distal shaft of the invention bends but is less likely to plastically deform than a steel distal shaft. Furthermore, a superelastic distal shaft may be advanced through tight curves in dilators and anatomy without permanent deformation. In typical embodiments, the proximal shaft is comprised of standard (non-superelastic) materials used in surgical devices and known to those skilled in the art, which provide columnar strength for pushability to enable advancement of the needle through a puncture in the tissue. The columnar strength also provides for tactile feedback to a user of the device, as explained in detail in U.S. Pat. No. 8,192,425, “RADIOFREQUENCY PERFORATION APPARATUS”, issued Jun. 5, 2012.

In one broad aspect, embodiments of the present invention include a needle comprising a distal shaft and a proximal shaft joined at a junction, the needle having a distal tip which includes an electrode for delivering energy to puncture a tissue, wherein the distal shaft is comprised of a superelastic material. In typical embodiments, the shaft includes a lumen for delivering and withdrawing fluids from a treatment site. Some embodiments of this broad aspect include a distal shaft comprised of both superelastic and non-superelastic material.

In another broad aspect, embodiments of the present invention include a needle comprising a distal shaft and a proximal shaft joined at a junction, the needle having a distal tip which includes an electrode for delivering energy to puncture a tissue, wherein the junction is comprised of a superelastic material. In some embodiments, the distal shaft is comprised of the same material as the proximal shaft.

With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of certain embodiments of the present invention only. Before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

FIG. 1 illustrates an assembly having a needle 20 that includes a proximal shaft 32, a distal shaft 42, a distal curved section 34, and a distal end 38 having an atraumatic electrode 36. In the embodiment of FIG. 1, distal curved section 34 includes both proximal shaft 32 and a portion of distal shaft 42, while in some alternative embodiments, distal curved section 34 includes only distal shaft 42. In such embodiments, distal curved section 34 may comprise all or part of the distal shaft i.e. the distal shaft 42 comprises distal curved section 34. Needle 20 also includes a hub/handle 22 with an attached electrical cable 26, and a fluid input 24. Electrical connector 28 is connected to the end of electrical cable 26 with heat shrink 30 covering the connection. Further details regarding needles used for puncturing tissue are found in U.S. Pat. No. 8,192,425, “RADIOFREQUENCY PERFORATION APPARATUS”, filed Oct. 1, 2007, which is incorporated by reference herein in its entirety.

Proximal shaft 32 and a distal shaft 42 together form an elongate member 70 which is made from electrically conductive material that is biocompatible. As used herein, ‘biocompatible’ refers to a material that is suitable for use within the body during the course of a surgical procedure. Such materials include stainless steels, copper, titanium and nickel-titanium alloys (for example, nitinol), amongst others. In typical embodiments, the proximal shaft 32 is made from stainless steel, such that it provides column strength for transmitting force, and the distal shaft 42 is made out of a nickel-titanium alloy, such as nitinol, such that it may provide flexibility to a distal portion of the elongate member 70. Embodiments wherein proximal shaft 32 is manufactured from stainless steel typically result in needle 20 having a similar amount of column strength to a device of the prior art, for example a mechanical perforator such as a Brockenbrough™ needle. This may be beneficial in that it may provide a familiar ‘feel’ to users who have used such devices in the past. In some embodiments comprising a distal curved section 34, the rectilinear section is made from stainless steel, such that it provides column strength to the elongate member 70, and the distal curved section 34 is made out of a nickel-titanium alloy, such as nitinol, such that it provides flexibility to the elongate member 70. In addition, the use of nitinol for distal curved section 34 is advantageous as the superelastic properties of this material helps in restoring the shape of the distal curved section 34 after the distal curved section is straightened out, for example when placed within a dilator.

The elongate member 70 has an electrical insulator 48 disposed on the external surface thereof with the electrode 36 substantially deprived from the electrical insulator 48. When a source of energy is coupled to the hub/handle 22 of the needle, the electrical insulator 48 substantially prevents leakage of energy along the length of the elongate member 70, thus allowing energy to be delivered from the electrode 36.

The electrical insulator 48 may be one of many biocompatible dielectric materials. Materials for electrical insulator 48 may include, but are not limited to, polytetrafluoroethylene (PTFE, Teflon®), parylene, polyimides, polyethylene terepthalate (PET), polyether block amide (PEBAX®), and polyetheretherketone (PEEK™), as well as combinations thereof. The thickness of the electrical insulator 48 may vary depending on the material used. Typically, the thickness of the electrical insulator is from about 0.02 mm to about 0.12 mm.

In some embodiments, the electrode 36 is located at the distal end of distal shaft 42, for example by being mechanically coupled to the distal shaft, while in other embodiments the electrode 36 is integral with the distal shaft 42. In some embodiments of needle 20, the electrode 36 is comprised of superelastic material, while in other embodiments, the electrode is comprised of non-superelastic material. In some specific embodiments, the electrode 36 is comprised of a non-superelastic material and is mechanically coupled to the distal shaft 42. In the example of FIG. 10, the electrode 36 comprises the distalmost portion of the distal shaft 42 of elongate member 70. That is, as shown in FIG. 10, if the electrical insulator 48 extends to a point that is substantially adjacent to the distal end 72 of the elongate member 70 (i.e. to the distal end 37 of the insulation), the exposed distalmost portion of elongate member 70 is operable as the electrode 36. In the embodiment of FIG. 10, the distal end 72 of the elongate member 70 includes the distal tip 21 of needle 20. In this embodiment, the electrode 36 is shaped as a hollow ring or cylinder. Having an open distal end 72, as shown in FIG. 10, may be desirable to allow for addition and/or removal of material from a site within a patient's body.

In further embodiments, such as shown in FIG. 11, the distal end 72 of the elongate member 70 is closed. For example, in some embodiments, it may be desirable for fluids to be injected radially from the elongate member 70, for example through side-port apertures in elongate member 70, substantially without being injected distally from the elongate member 70. In these embodiments, a closed distal end 72 may facilitate radial injection of fluid while preventing distal injection.

As shown in FIG. 11, an external component 80, for example an electrode tip, may be operatively coupled to the distal end 72. In this embodiment, the exposed portion of the distal region of distal shaft 42, as well as the external component 80, serves as the electrode 36. In the embodiment of FIG. 11, the external component 80 includes the distal tip 21 of needle 20. In some alternative embodiments, e.g. distal shaft 42 is closed-ended hypotube, the distal end 72 of elongate member 70, rather than a separate external component, is closed and is operable as the electrode 36. In other alternative embodiments, a metal plug (or metal particles) is placed in the distal end of a hollow distal shaft 42, and the distal shaft and plug are welded to thereby fuse them together.

FIG. 2 illustrates a cross sectional side view of the distal portion of a needle 20 having a proximal shaft 32 comprised of a material that provides columnar strength for pushability (e.g. stainless steel or titanium), and a distal shaft 42 comprised of a superelastic material (e.g. a nickel-titanium alloy or a titanium-niobium-tin (TiNbSn) alloy). Under normal use, the superelastic material of the distal shaft 42 bends and returns to its original shape without permanently deforming. Distal shaft 42 typically forms a smooth radius (i.e. a smooth curve) when subjected to a mechanical load. In typical embodiments of needle 20, proximal shaft 32 is comprised of a rigid metal and distal shaft 42 is comprised of a biocompatible superelastic metal known to those skilled in the art. In a specific embodiment, proximal shaft 32 is comprised of stainless steel having a modulus of elasticity of about 180 to 200 GPa, and distal shaft 42 is comprised of a nickel-titanium alloy (e.g. Nitinol®) having a modulus of elasticity of about 40 to 75 GPa.

The embodiment of distal shaft 42 of FIG. 2 is substantially straight, while that of FIG. 1 has a curve. In some alternative embodiments, the distal portion of distal shaft 42 has a partial spiral shape (or pigtail shape) when the needle 20 is not being manipulated that may be used to anchor the distal end 38 of the needle in a location in a patient's body, for example, in the left atrium. In embodiments with a distal curved section 34, the partial spiral will form a curve within a curve.

The embodiment of FIG. 2 further includes electrical insulator 48 outside of the proximal and distal shafts, leaving electrode 36 electrically exposed. An aperture or side-port 46 is in fluid communication with lumen 40, whereby the needle 20 may be used for delivering fluid, withdrawing fluid, and/or monitoring pressure. In some embodiments, electrode 36 is comprised of a radiopaque material to provide an imaging marker 44 for positioning the distal end 38 of the device.

In some embodiments, proximal shaft 32 has a length of about 50 cm to about 100 cm, and an outer diameter of about 1.15 mm to about 1.35 mm. In some embodiments, the distal shaft 42 has a length of about 2.5 cm to about 10 cm, and an outer diameter of about 0.40 mm to about 0.80 mm. Further details regarding needles used for puncturing tissues and the curves in such needles are found in U.S. Pat. No. 8,679,107, “RADIOFREQUENCY PERFORATION APPARATUS”, filed May 10, 2012, which is herein incorporated-by-reference in its entirety.

Making reference to FIGS. 1 and 2, some embodiments of needle 20 include a distal curved section 34 having a tube-in-tube configuration wherein the proximal shaft 32 overlaps the distal shaft 42 such that the distal shaft is partially nested within the proximal shaft. In tube-in-tube embodiments in which distal curved section 34 includes both proximal shaft 32 and distal shaft 42, the curve of proximal shaft 32 and distal shaft 42 should have the same radius (i.e. the curves should be the same) across the overlap. In some specific embodiments, the curve has a radius of about 5.6 cm (about 2.2 inches). The proximal shaft 32 and the distal shaft 42 are substantially tubular and joined in any suitable manner, for example welding, soldering, friction fitting, or the use of adhesives, among other possibilities.

The usable needle length (i.e. the length of the needle's shaft that may be inserted into a patient's body) of such embodiments is the combined length of proximal shaft 32 and distal shaft 42 (after being joined) that extends distal to hub/handle 22. Some embodiments of needle 20 have a useable length of about 56 cm to about 98 cm. Some specific embodiments have useable lengths of about 56+0.5/−0 cm, 71±0.5 cm, 89±0.5 cm, or 98±0.5 cm. Some embodiments have a distal shaft 42 with a length of about 25 to 35 mm and some specific embodiments have a distal shaft of about 30±2 mm. In some embodiments of needle 20, distal shaft 42 extends about 13 to 17 mm distal of proximal shaft 32, and in some specific embodiments, distal shaft 42 extends about 15+1/−0 mm.

With respect to the diameters of needle 20, some embodiments comprise distal shaft 42 having an inner diameter of about 0.015 to 0.022 inches (0.38 to 0.59 mm), an outer diameter of about 0.023 to 0.029 inches (0.58 to 0.74 mm), and a proximal shaft 32 having an inner diameter of about 0.025 to 0.031 inches (0.64 to 0.79 mm), and an outer diameter of about 0.038 to 0.055 inches (0.97 to 1.4 mm). Some specific embodiments comprise distal shaft 42 having an inner diameter of about 0.017+0.001/−0.0005 inches (0.43+0.025/−0.013 mm), an outer diameter of about 0.025+0.0005/−0.000 inches (0.64+0.013/−0.0 mm), and a proximal shaft 32 having an inner diameter of about 0.027±0.0015 inches (0.69±0.038 mm), and an outer diameter of about 0.042+0.0005/−0.0 inches (1.1+0.012/−0.0 mm). Some other specific embodiments comprise distal shaft 42 having an inner diameter of about 0.020±0.0008 inches (0.51±0.020 mm), an outer diameter of about 0.028+0.0004 inches (0.71+0.010 mm), and a proximal shaft 32 having an inner diameter of about 0.028+0.002/−0.0 inches (0.71+0.051/−0.0 mm), and an outer diameter of about 0.047±0.0006 inches (1.2±0.015 mm).

In some alternative embodiments, distal end 38 comprises a sharp distal tip for mechanically puncturing tissue. Some alternative embodiments do not include a lumen or side-port (or aperture). Furthermore, some alternative embodiments comprise a single shaft comprised of a superelastic metal.

The embodiment of needle 20 in FIG. 2 has a tube-in-tube configuration wherein the inner diameter of proximal shaft 32 accommodates the outer diameter of distal shaft 42. FIGS. 3, 4, and 5 illustrate alternative tube configurations.

FIG. 3 shows a cross-sectional side view of the distal portion of a needle 20 wherein proximal shaft 32 and distal shaft 42 are joined at joint 50 and have an end-to-end tube configuration with a taper 52. FIG. 4 shows a needle 20 having an end-to-end tube configuration without a taper.

FIG. 5 shows a cross-sectional side view of the distal portion of a needle wherein the junction comprises an interlocking joint 50. The embodiment of FIG. 5 further includes an imaging marker 44 that the user may view under imaging to determine the location of the joint 50 within a patient's body. The distal shaft 42 and proximal shaft 32 may be joined by gluing, welding, or other means known to those skilled in the art. In one embodiment, curvatures are imparted into a superelastic distal shaft 42 using a thermal shape-setting process, and into a non-superelastic proximal shaft 32 using a mechanical process (i.e. a process without heating).

FIGS. 6, 7, and 8 illustrate embodiments of needle 20 comprising a proximal shaft 32 sufficiently rigid to provide pushability to the needle, a distal shaft 42 comprised of a non-superelastic material, and a superelastic hinge connecting or joining the proximal and distal shafts. In some embodiments, distal shaft 42 is comprised of the same material as proximal shaft 32.

FIG. 6 illustrates an embodiment of a needle including a junction comprising an overlapping superelastic hinge 60. Overlapping superelastic hinge 60 overlaps and is joined to proximal shaft 32 and distal shaft 42. The example of FIG. 6 includes electrical insulator 48 which is flowed into the space between proximal shaft 32 and distal shaft 42.

FIG. 7 is a cross-sectional side view of the distal portion of a needle having a junction comprising an end-to-end superelastic hinge 62 connecting the proximal and distal shafts.

FIG. 8 illustrates an embodiment of a needle having a junction comprising a combined overlapping and end-to-end superelastic hinge which includes an overlapping superelastic hinge 60 portion and an end-to-end superelastic hinge 62 portion. Overlapping superelastic hinge 60 portion is on the outside of the proximal and distal shafts, and electrical insulator 48 covers the shafts and hinges to provide a smooth outer surface. The overlapping portion and end-to-end portion may be the same material or different materials.

FIG. 9 is a cross-sectional side view of the distal portion of a needle having a hybrid distal shaft. Proximal shaft 32 is sufficiently rigid to provide pushability to the needle. The distal shaft 42 is comprised of an inner layer 42 b and an outer layer 42 a, with one layer being comprised of superelastic material and the other layer being comprised of non-superelastic material. While the embodiment of FIG. 9 includes inner layer 42 b and outer layer 42 a being about the same thickness, embodiments of the needle include the superelastic layer comprising from about 10 to 90 percent of the thickness of distal shaft 42. The thickness of the non-superelastic material may be varied to adjust the rigidity of the distal shaft. In some alternative embodiments, distal shaft 42 includes more than two layers of material.

The example of FIG. 9 includes the proximal and distal shaft having an overlapping tube-in-tube configuration. Some embodiments having the hybrid distal shaft comprise the proximal and distal shaft being joined in one of the other configurations described above, or other configurations know to those skilled in the art.

FIG. 12, in a partially cut-away view, illustrates an embodiment of the needle 20 having an internal support wire 84 and a spiral cut 82 in distal shaft 42. Proximal shaft 32 and distal shaft 42 are joined at joint 50. In the embodiment of FIG. 12, proximal shaft 32 is typically made of stainless steel and support wire 84 is made of nitinol. Spiral cut 82 extends distally from joint 50 and stops proximally of side-port 46. Spiral cut 82 increases the flexibility of distal shaft 42. In some embodiments, distal shaft 42 is comprised of a continuously laser-cut nitinol hypotube. While the proximal shaft 32 of FIG. 12 is straight, in some alternative embodiments it includes a curved portion or a bend for increased torqueability. The distal shaft 42 of FIG. 12 is curved (when not forced into another shape), but some alternative embodiments of distal shaft 42 are straight or have other curved configurations.

In FIG. 12, support wire 84 extends proximally from imaging marker 44. In some alternative embodiments without imaging marker 44, support wire 84 extends proximally from electrode 36. In general, support wire 84 extends proximally from a distal end 38 of the needle at least within the lumen of distal shaft 42. Support wire 84 provides support for distal shaft 42. Support wire 84 can be made of steel, nitinol, or other metals, and is typically concentrically aligned with distal shaft 42. In some embodiments, distal shaft 42 and support wire 84 are both comprised of a superelastic material such as nitinol to provide for shape retention. Details about the support wire 84 and spiral cut 82 are found in U.S. application Ser. No. 14/851,353, entitled “Electrosurgical device having a lumen”, filed Sep. 11, 2015, and U.S. application Ser. No. 14/851,412, entitled “Medical device having a support structure”, filed September 11, which are incorporated by reference herein in their entirety.

The transverse cross-sectional shape of the elongate member 70 (proximal shaft 32 and distal shaft 42) of the different embodiments may take any suitable configuration, and the invention is not limited in the regard. For example, the transverse cross-sectional shape of embodiments of the elongate member 70 is substantially circular, ovoid, oblong, or polygonal, among other possibilities. Furthermore, the cross-sectional shape may vary along the length of the elongate member. For example, in one embodiment, the cross-sectional shape of the proximal region is substantially circular, while the cross-sectional shape of the distal region is substantially ovoid.

In one broad aspect, needle 20 is usable to deliver energy to a target site within a body of a human or animal to perforate or create a void or channel in a material at the target site. Further details regarding delivery of energy to a target site within the body are found in U.S. patent application Ser. No. 10/347,366 (filed on Jan. 21, 2003), Ser. No. 10/760,749 (filed on Jan. 21, 2004), Ser. No. 10/666,288 (filed on Sep. 19, 2003), and Ser. No. 11/265,304 (filed on Nov. 3, 2005), and U.S. Pat. No. 7,048,733 (application Ser. No. 10/666,301, filed on Sep. 19, 2003) and U.S. Pat. No. 6,565,562 (issued on May 20, 2003), all of which are incorporated herein by reference.

In one specific embodiment, the target site may comprise a tissue within the heart of a patient, for example, the atrial septum of the heart. In such an embodiment, the user may access the target site from the inferior vena cava (IVC) via the femoral vein. In alternative embodiments, the needle may be used to puncture or provide a channel through a graft material or a blockage of an anatomical lumen.

In other embodiments, methods of the present invention may be used for treatment procedures involving other regions within the body, and the invention is not limited in this regard. For example, rather than the atrial septum, embodiments of devices, systems and methods of the present invention may be used to treat pulmonary atresia. In some such embodiments, a sheath is introduced into the vascular system of a patient, and guided to the heart. A dilator is then introduced into the sheath, and advanced towards the heart, where it is positioned against the pulmonary valve. Needle 20 is then introduced into the proximal region of the dilator, and guided therethrough, such that it is also positioned against the pulmonary valve. Energy is then delivered from the energy source, through the electrode 36 of needle 20, to the pulmonary valve, such that a perforation or void is created therethrough, as described hereinabove. When the needle has passed through the valve, the user may apply a force, for example in a substantially cranial direction, to the proximal region of the dilator. The force may be transmitted to the distal region of the dilator, such that the distal region of the dilator enters the perforation and advances through the pulmonary valve. As regions of the dilator of larger diameter pass through the perforation, the perforation or channel becomes dilated.

In other applications, embodiments of a device of the present invention may be used to create voids or channels within or through other tissues of the body, for example within or through the myocardium of the heart. In other embodiments, the device may be used to create a channel through a fully or partially occluded lumen within the body. Examples of such lumens may include, but are not limited to, blood vessels, the bile duct, airways of the respiratory tract and vessels and/or tubes of the digestive system, the urinary tract and/or the reproductive system. In such embodiments, the device may be positioned such that the electrode of the device is substantially adjacent the material to be perforated. Energy may be delivered from an energy source, through the electrode 36, to the target site such that a void, perforation, or channel is created in or through the tissue.

The embodiments of the invention described above are intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the broad scope of the appended claims. All publications, patents, and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. 

We claim:
 1. A needle for puncturing tissue comprising: a rigid proximal shaft including a rigid metal tube; a flexible distal shaft joined to the proximal shaft, the flexible distal shaft including a metal tube with a longitudinally extending spiral cut therein; an electrical insulator is disposed on an external surface of the rigid proximal shaft and the flexible distal shaft wherein the electrical insulator covers the longitudinally extending spiral cut; and a distal tip which includes an electrode which is rounded and atraumatic for delivering energy to puncture a tissue.
 2. The needle of claim 1, wherein the distal tip is rigid.
 3. The needle of claim 2, wherein the distal shaft comprises a superelastic material and the electrode comprises a non-superelastic material.
 4. The needle of claim 2, wherein the proximal shaft and distal tip are more rigid than the distal shaft.
 5. The needle of claim 1, wherein the proximal shaft comprises a material that provides columnar strength for pushability and has a modulus of elasticity of about 180 to 200 GPa.
 6. The needle of claim 1, wherein the proximal shaft and the distal shaft are made from electrically conductive material and the proximal shaft, distal shaft and distal tip are electrically connected.
 7. The needle of claim 6, wherein the distal shaft is comprised of both a superelastic material and a non-superelastic material.
 8. The needle of claim 7, wherein the distal shaft comprises an inner layer and an outer layer, wherein one of the inner layer or the outer layer is comprised of the superelastic material and the other of the inner layer or the outer layer is comprised of the non-superelastic material.
 9. The needle of claim 6, wherein the rigid metal tube is comprised of a stainless steel.
 10. The needle of claim 1, wherein the distal shaft comprises a curved section.
 11. The needle of claim 10, wherein the proximal shaft comprises a curved section with the same radius as the curved section of the distal shaft.
 12. Medical apparatus comprising: a sheath comprising a sheath lumen; a dilator configured to fit in the sheath lumen, the dilator comprising a dilator lumen; and a needle for puncturing tissue configured to fit in the dilator lumen, the needle comprising a rigid proximal shaft including a rigid metal tube, a flexible distal shaft joined to the proximal shaft, the flexible distal shaft including a metal tube with a longitudinally extending spiral cut therein, an electrical insulator is disposed on an external surface of the rigid proximal shaft and the flexible distal shaft wherein the electrical insulator covers the longitudinally extending spiral cut, and a distal tip which is rounded and atraumatic having an electrode for delivering energy to a tissue; wherein the flexible distal shaft is sufficiently flexible to conform to a shape of the dilator and sheath assembly.
 13. The medical apparatus of claim 12, wherein the distal tip of the needle is rigid.
 14. The medical apparatus of claim 13, wherein the distal shaft of the needle comprises a superelastic material and the distal tip comprises a non-superelastic material.
 15. The medical apparatus of claim 13, wherein the proximal shaft of the needle and distal tip of the needle are more rigid than the distal shaft of the needle.
 16. The medical apparatus of claim 12, wherein the flexible distal shaft of the needle is sufficiently flexible to conform to a lumen of at least one of the dilator and the sheath.
 17. The medical apparatus of claim 12, wherein the distal shaft of the needle comprises a curved section.
 18. The need-le medical apparatus of claim 17, wherein the proximal shaft of the needle comprises a curved section with the same radius as the curved section of the distal shaft of the needle.
 19. The medical apparatus of claim 12, wherein the distal tip of the needle protrudes from the distal end of the sheath and dilator if the needle is advanced through the sheath and dilator.
 20. A method for puncturing tissue, comprising introducing a sheath into a vascular system; introducing a dilator into the sheath and advancing to position the dilator against a tissue; introducing a needle into the proximal region of the dilator, the needle comprising a rigid proximal shaft including a rigid metal tube, a flexible distal shaft joined to the proximal shaft, the flexible distal shaft including a metal tube with a longitudinally extending spiral cut therein, an electrical insulator is disposed on an external surface of the rigid proximal shaft and the flexible distal shaft wherein the electrical insulator covers the longitudinally extending spiral cut, and a distal tip which is rounded and atraumatic having an electrode for delivering energy to a tissue; advancing the needle through the dilator to the tissue wherein the flexible distal shaft is sufficiently flexible to conform to a shape of the dilator; and delivering energy from an energy source through the electrode of the needle whereby the energy creates a puncture. 